1. Field of the Invention
The present invention relates to a voltage measurement device for measuring battery voltages of serially connected battery blocks, and an electric vehicle having the voltage measurement device.
2. Description of the Related Art
A high output power source of a few hundred volts to be mounted in an electric vehicle, such as a hybrid electric vehicle or the like, comprises a plurality of serially connected battery modules, such as a nickel-metal hydride (nickel-metalhydride) secondary battery, a lithium ion secondary battery, or the like. A battery voltage of a secondary battery is used as a parameter to control charge/discharge of such a secondary battery.
Japanese Patent Laid-open Publication No. Hei 11-248755 discloses a measurement device for measuring a battery voltage of serially connected battery blocks in battery block units.
Japanese Patent Laid-open Publication No. 2005-328642 discloses a device for equalizing the capacitance of battery blocks based on the battery voltages measured in battery block units.
The device for measuring a battery voltage in battery block units as disclosed in the above-mentioned Japanese Patent Laid-open Publications No. Hei 11-248755 and No. 2005-328642 cannot measure the battery voltage of some serially connected battery blocks in the event that the potential detection line is disconnected or the like. This may cause a problem, for example, in calculation of the capacitance of the respective battery blocks. However, if measurement target secondary battery is functioning normally, it may sometimes be desirable, for example, for the secondary battery to continuously charged/discharged so that the equalization control can be continued.
The present invention aims to provide a voltage measurement device for measuring a battery voltage of a secondary battery formed by serially connecting a plurality of battery blocks, which can measure a battery voltage in battery block units should the potential detection line be disconnected or the like.